PROJECT SUMMARY Scleroderma (systemic sclerosis; SSc) is an autoimmune disease of unknown etiology that is characterized by vascular dysfunction, fibrosis, and inflammation. One in three patients dies within 10 years of diagnosis, giving SSc the highest case fatality rate of any systemic autoimmune disease. A lack of biologically-relevant SSc disease models has created a critical unmet need for more efficient preclinical drug screening models that can provide faster, more cost-effective ways of predicting the success or failure of drugs designed to treat SSc. Recent advances in tissue engineering have resulted in 3-D skin tissue-based disease models that can closely mimic SSc in humans. This advancement will shorten the preclinical drug development timeline, save animal lives, increase drug success rates, and inform FDA decision-making for the development of new and effective disease therapeutics. In phase-I SBIR work, the Celdara Medical research team developed 3-D skin-like tissue models that accurately recapitulate the SSc phenotype and are an important advancement over the currently available monolayer, 2-D tissue cultures. Phase-II work is now proposed to develop this into a commercial, pre- clinical drug screening platform, named SclerEx. By developing 3-D skin models at Celdara, this promising in vitro system can now be paired with Celdara?s existing portfolio of SSc diagnostics and SSc, fibrosis, and cancer drug development efforts. It can also be provided to Celdara?s pharma partners for pre-clinical drug testing of anti-fibrotic compounds that exist in their development pipelines. This work will leverage SclerEx skin-like models for drug screening, which will advance complex tissue models for other organ systems, such as lung and esophagus. By using multiple, patient-derived cell types to optimize 3-D tissues to establish robust, SSc-specific, 3-D tissue models that can serve as preclinical drug screening platforms for new therapeutic agents for SSc, this project will advance the identification of anti-fibrotic therapies. The aims of the work proposed are to: (1) evaluate the reproducibility of the previously optimized 3-D tissue model for SSc by performing assay validation and consistent benchmark measures that are reproducible and reliable; (2) demonstrate and evaluate the utility of the model for drug screening by performing proof-of-concept screening using known SSc therapies and therapies currently in clinical trials; and (3) identify and control for the circulating factor(s) in plasma/sera that result in increased skin thickness and/or impact monocyte differentiation by Luminex assays or high-throughput protein screening, so it will generate a highly reproducible 3-D tissue model system.